The present invention relates to a machine for retreading tires; the invention concerns, in particular, a buffer as well as a combined machine further containing means for application and rolling down of the treads.
It is known that most tires can be retreaded, that is, it is possible--after normal wear of the tread --to replace that tread and even some of the plies reinforcing the belt of the tire. Such operations are very common for truck tires; they can be carried out in factories or at relatively large shops.
Numerous machines designed to remove remains of the tread from worn tires, a "detreading" operation, have been proposed. Among them, many use a buffer to carry out that detreading.
Such a buffer consists of a series of blades containing cutting teeth on the outside and arranged side by side. Such a machine is disclosed in U.S. Pat. No. 4,116,256. Those machines often contain complex adjustments for enabling the whole variety of necessary buffing profiles to be obtained.
More or less complex machines making it possible to reduce the different detreading or buffing and retreading operations, without resorting to overly frequent adjustments or repairs, have also been imagined. For example, U.S. Pat. No. 4,036,677 and French Patent 2,271,037, based on an Italian priority of May 14, 1974, describe an "all-purpose" machine comprising a rotary chuck on which the tire to be detreaded-retreaded is mounted, carcass buffing tools, a coaxial radial expander with the chuck, which brings the new tread around the carcass in the form of a ring, and means for rolling down in order to make the new tread adhere to the carcass.
The tire treated remains on the same chuck during buffing and molding, that is, application of the new tread, but without any interaction of the different parts of the machine, which results in a redundancy of drive units, and the need to mark several times the respective positions of the carcass and of the tread of the tire in the course of the successive operations.
The new tread can also be cut to the desired length and placed continuously on the carcass and then butted, that is, its two ends, once joined, are welded; a machine of that type is described in patent EP 0,704,296, but that machines carries out only the application of the new tread on the tire, the so-called "molding" operation.